Induction of c-fos-like protein in spinal cord neurons following sensory stimulation

It has been suggested that the proto-oncogenes c-fos and c-myc participate in the control of genetic events which lead to the establishment of prolonged functional changes in neurons. Expression of c-fos and c-myc are among the earliest genetic events induced in cultured fibroblast and phaeochromocytoma cell lines by various stimuli including growth factors, peptides and the intracellular second messengers diacylglycerol, cAMP and Ca2+. We report here that physiological stimulation of rat primary sensory neurons causes the expression of c-fos-protein-like immunoreactivity in nuclei of postsynaptic neurons of the dorsal horn of the spinal cord. Activation of small-diameter cutaneous sensory afferents by noxious heat or chemical stimuli results in the rapid appearance of c-fos-protein-like immunoreactivity in the superficial layers of the dorsal horn. However, activation of low-threshold cutaneous afferents results in fewer labelled cells with a different laminar distribution. No c-fos induction was seen in the dorsal root ganglia, gracile nucleus or ventral horn. Thus, synaptic transmission may induce rapid changes in gene expression in certain postsynaptic neurons.     

DNA sequence and analysis of human chromosome 9

Chromosome 9 is highly structurally polymorphic. It contains the largest autosomal block of heterochromatin, which is heteromorphic in 6-8% of humans, whereas pericentric inversions occur in more than 1% of the population. The finished euchromatic sequence of chromosome 9 comprises 109,044,351 base pairs and represents >99.6% of the region. Analysis of the sequence reveals many intra- and interchromosomal duplications, including segmental duplications adjacent to both the centromere and the large heterochromatic block. We have annotated 1,149 genes, including genes implicated in male-to-female sex reversal, cancer and neurodegenerative disease, and 426 pseudogenes. The chromosome contains the largest interferon gene cluster in the human genome. There is also a region of exceptionally high gene and G + C content including genes paralogous to those in the major histocompatibility complex. We have also detected recently duplicated genes that exhibit different rates of sequence divergence, presumably reflecting natural selection.     

Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants

Most of the 470-million-year history of plants on land belongs to bryophytes, pteridophytes and gymnosperms, which eventually yielded to the ecological dominance by angiosperms 90 Myr ago. Our knowledge of angiosperm phylogeny, particularly the branching order of the earliest lineages, has recently been increased by the concurrence of multigene sequence analyses. However, reconstructing relationships for all the main lineages of vascular plants that diverged since the Devonian period has remained a challenge. Here we report phylogenetic analyses of combined data--from morphology and from four genes--for 35 representatives from all the main lineages of land plants. We show that there are three monophyletic groups of extant vascular plants: (1) lycophytes, (2) seed plants and (3) a clade including equisetophytes (horsetails), psilotophytes (whisk ferns) and all eusporangiate and leptosporangiate ferns. Our maximum-likelihood analysis shows unambiguously that horsetails and ferns together are the closest relatives to seed plants. This refutes the prevailing view that horsetails and ferns are transitional evolutionary grades between bryophytes and seed plants, and has important implications for our understanding of the development and evolution of plants.